Poly(arylene thioether) (hereinafter abbreviated as "PATE") represented by poly(p-phenylene sulfide) is known as a polymer having a high crystalline melting point and excellent heat resistance, solvent resistance and mechanical properties.
However, PATE is restricted in its application to uses for which flexibility is required due to its high crystalline melting point and glass transition temperature, or has a drawback to its development into fields used as a solution due to its high solvent resistance. It has therefore been desired to improve the above-described problems while retaining the good heat resistance of PATE.
The present inventors carried out an investigation with a view toward providing improved arylene thioether copolymers by copolymerizing with an arylene thioether component, which is a constituent for PATE, another component.
The present inventors previously found that when an alkali metal sulfide is caused to act on PATE in a polar solvent, the principal chain of PATE is cut to depolymerize PATE, whereby a compound having at least one alkali thiolate group can be obtained (Japanese Patent Application Laid-Open No. 7334/1992 and U.S. patent application No. 07/686,972). The average polymerization degree of the compound obtained by this depolymerization process can be adjusted to any level ranging from oligomers to polymers relatively high in molecular weight, and the compound can be expected to use as a raw material for various syntheses because it has at least one alkali thiolate group as an active group. In addition, it is expectable to provide a copolymer having a uniform composition when using an oligomer (average polymerization degree: about 50 or lower) obtained by this depolymerization process as a copolymerizable component with other components because the molecular weight distribution of the oligomer is relatively even.
In Japanese Patent Application Laid-Open No. 140233/1990, there is disclosed a process in which a poly(phenylene sulfide) is reacted with an alkali metal sulfide at 150.degree.-230.degree. C. in a polar aprotic solvent, thereby producing a poly(phenylene sulfide) having a thiolate or thiol group on at least one terminal thereof. However, this polymer is not a polymer obtained by depolymerization, and is used for forming a block or a graft copolymer which serves as a compatibilizer by melting and mixing it with various kinds of polymers.
In Makromol. Chem., Macromol. Symp., 26, 1-8 (1989) and Makromol. Chem., 191, 815-828 (1990), there is disclosed a process in which p-dichlorobenzene is reacted with an excess amount of sodium sulfide to obtain a polymer having an alkali thiolate group on at least one terminal thereof and the thus-obtained polymer is further reacted with p-chlorobenzoic acid, thereby producing a carboxylic acid containing polymer. Further, in Polymer Bulletin, 4, 459-466 (1981) and Die Angewandte Makromolekulare Chemie, 145/146, 37-68 (1986), there is disclosed carboxylic acid containing p-phenylene thioether oligomers. Furthermore, France Patent No. 2,470,780 and Polymer Bulletin, 6, 477-484 (1982) disclose a process for the production of copolymers by reacting a carboxylic acid containing p-phenylene thioether oligomer with a diol. None of these references disclose a production process of copolymers by using an oligomer having at least one alkali thiolate, which is obtained by causing an alkali metal sulfide to act on PATE to depolymerize PATE.